automaton.filter.ipynb

Kernel: Python 3

automaton.filter(states)

Return a subautomaton such that their states are in the input states set.

Postcondition:

• The result automaton is subautomaton of input automaton.

• The states of automaton are in the input states set.

See also:

• automaton.accessible

• automaton.coaccessible

• automaton.trim

Examples

import vcsn

%%automaton -s aut
context = "lal_char(a), b"
0 -> 1 a
1 -> 0 a
1 -> $
1 -> 2 a
3 -> 0 a
4 -> 3 a
0 -> 3 a
$ -> 0
3 -> 5 a

To keep only states $0, 1, 2 , 3$:

aut.filter([0, 1, 2, 3])

"Keeping" a non-existing state is not an error:

aut.filter([0, 1, 7])

Calls to filter can be filtered:

a1 = aut.filter([0, 1, 2, 3, 4]).filter([0, 1, 3, 5])
a1

but it is less efficient than filtering on the intersection. This is on purpose: the outter automaton has a view on the filtered automaton.

a2 = aut.filter(list(set([0, 1, 2, 3, 4]) & set([0, 1, 3, 5])))
print(a1.info()['type'])
print(a2.info()['type'])
print(a1.is_isomorphic(a2))

filter_automaton<filter_automaton<mutable_automaton<letterset<char_letters(a)>, b>>>
filter_automaton<mutable_automaton<letterset<char_letters(a)>, b>>
True

We can filter a transposed automaton:

trans = aut.transpose()
trans

trans.filter([0, 1, 2, 3])